package com.ycyoes.demos.geetime.algorithm.chapter5;

/**
 * 泛型数组
 * 
 * @author ycyoes
 * @date 2020-03-21 23:49
 * @param <T>
 */
public class GenericArray<T> {
	private T[] data;
	private int size;
	
	//根据传入容量，构造Array
	public GenericArray(int capacity) {
		data = (T[])new Object[capacity];
		size = 0;
	}
	
	//无参构造方法，默认数组容量为10
	public GenericArray() {
		this(10);
	}
	
	//获取数组容量
	public int getCapacity() {
		return data.length;
	}
	
	//获取当前元素个数
	public int count() {
		return size;
	}
	
	//判断数组是否为空
	public boolean isEmpty() {
		return size == 0;
	}
	
	//修改index位置的元素
	public void set(int index, T e) {
		checkIndex(index);
		data[index] = e;
	}
	
	//获取对应index位置的元素
	public T get(int index) {
		checkIndex(index);
		return data[index];
	}
	
	//查看数组是否包含元素e
	public boolean contains(T e) {
		for (int i = 0; i < size; i++) {
			if (data[i].equals(e)) {
				return true;
			}
		}
		return false;
	}
	
	//获取对应元素的下标，未找到，返回-1
	public int find(T e) {
		for (int i = 0; i < size; i++) {
			if (data[i].equals(e)) {
				return i;
			}
		}
		return -1;
	}
	
	//在index位置，插入元素e,时间复杂度O(m+n)
	public void add(int index, T e) {
		checkIndexForAdd(index);
		//如果当前元素个数等于数组容量，则将数组扩容为原来的2倍
		if (size == data.length) {
			resize(2 * data.length);
		}
		for(int i = size - 1; i >= index; i--) {
			data[i + 1] = data[i];
		}
		data[index] = e;
		size++;
	}
	
	//向数组头插入元素
	public void addFirst(T e) {
		add(0, e);
	}
	
	//向数组尾插入元素
	public void addLast(T e) {
		add(size, e);
	}
	
	//删除index位置的元素，并返回
	public T remove(int index) {
		checkIndex(index);
		
		T ret = data[index];
		for(int i = index + 1; i < size; i++) {
			data[i - 1]  =  data[i];
		}
		//将最后一个元素置为空，然后长度减一
		data[size] = null;
		size--;
		
		//缩容
		if (size == data.length / 4 && data.length / 2 != 0) {
			resize(data.length / 2);
		}
		
		return ret;
	}
	
	//删除第一个元素
	public T removeFirst() {
		return remove(0);
	}
	
	//删除末尾元素
	public T removeLast() {
		return remove(size - 1);
	}
	
	//从数组中删除指定元素
	public void removeElement(T e) {
		int index = find(e);
		if (index != -1) {
			remove(index);
		}
	}
	
	public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append(String.format("Array size = %d, capacity = %d \n", size, data.length));
        builder.append('[');
        for (int i = 0; i < size; i++) {
            builder.append(data[i]);
            if (i != size - 1) {
                builder.append(", ");
            }
        }
        builder.append(']');
        return builder.toString();
    }
	
	//扩容方法，时间复杂度O(n)
	private void resize(int capacity) {
		T[] newData = (T[])new Object[capacity];
		for (int i = 0; i < size; i++) {
			newData[i] = data[i];
		}
		data = newData;
	}
	
	private void checkIndexForAdd(int index) {
		if (index < 0 || index > size ) {
			throw new IllegalArgumentException("remove failed! Required index >= 0 and index < =size.");
		}
	}
	
	private void checkIndex(int index) {
		if (index < 0 || index >= size) {
			throw new IllegalArgumentException("Add failed! Required index >= 0 and index < size.");
		}
	}
}
